2 3-epithiopropyl n n-dialkyl-thiolcar-bamates and use as herbicid

ABSTRACT

BY A METHOD OF SYNTHESIS BASED ON A SECONDARY AMINE, CARBON DISULFIDE AND EPICHLOROHYDRIN THERE ARE PRODUCED 2,3-EPITHIOPROPYL N,N-DIALKYLTHIOLCARBAMATES WHICH ARE USED AS SELECTIVE HERBICIDES, PARTICULARLY IN PRE-EMERGENT CONTROL OF GRASSES SUCH AS BROE AND VOLUNTEER OATS.

United States Patent 3,634,457 2,3-EPITHIOPROPYL N,N-DIALKYL-THIOLCAR-BAMATES AND USE AS HERBICIDES William Carter Doyle, Jr., ShawneeMission, Kans., as-

signor to Gulf Research & Development Company, Pittsburgh, Pa. NoDrawing. Original application Mar. 24, 1967, Ser. No. 625,603, nowPatent No. 3,510,290, dated May 5, 1970. Divided and this applicationJuly 30, 1969, Ser. No.

Int. C1. C07(] 59/00 US. Cl. 260-327 E Claims ABSTRACT OF THE DISCLOSUREBy a method of synthesis based on a secondary amine, carbon disulfideand epichlorohydrin there are produced 2,3-epithiopropylN,N-dialkylthiolcarbamates which are used as selective herbicides,particularly in pre-emergent control of grasses such as brome andvolunteer oats.

SUMMARY OF INVENTION This application is a division of US. Ser. No.625,603 filed Mar. 24, 1967, now US. Pat. 3,510,290:

It is 'known that reaction of carbon disulfide with a secondary aminereadily produces the amine salt of a corresponding dithiocarbamate, asillustrated below:

The product possesses very selective herbicidal activity against a fewgrasses, particularly brome and oats, and is readily converted to thecorresponding epithio ester which possesses similar herbicidal activityand greater chemical stability:

The highly selective pre-emergent phytotoxicity of the novelcompositions is partlcularly useful for application at the time ofplanting such crops as alfalfa and corn.

3,634,457. Patented Jan. 11, 1972 Certain specific compounds of thegroup may also be applied at the time of planting soybeans and cotton.The preferred selective pre-emergent herbicides are 2,3-epithiopropylN,N-dihydrocarbon substituted thiolcarbamates in which the twohydrocarbon substituents contain a total of less than ten carbon atoms.The hydrocarbon substituents may include alkyl, cycloalkyl fromcyclopropyl to cyclohexyl and lower alkenyl groups.

DETAILED DESCRIPTION (I) Synthesis methods The compounds of the series,2,3-epithiopropyl N,N- dialkylthiolcarbamates, are prepared by twogeneral methods, one a three-step process, with isolation ofintermediates and the other essentially a single-step process.

The initial low temperature reaction is believed to include reaction ofepichlorohydrin with N,N-dialkylithiocar-bamic acid.

The reaction of epichlorohydrin with a salt (which may also be a metalsalt, as well as an amine salt) appears to require a higher temperaturethan reaction with the acid.

In an experiment in which both routes were used to prepare the sameN,N-diethyl thiolcarbamate compound, the'yields were roughly equivalent.In syntheses based on morpholine, dicyclohexylamine or isopropylcyclohexylamine as starting materials, Method B has been found to be theonly successful route, with the dithiocarbamate salt being the soleproduct obtained in the first step of Method A, rather than the morereactive free acid.

Intermediates I and II are isolable, though not easily purified. I isthermally unstable, rearranging to II in a matter of several hours toseveral days, depending on the nature of the N substituents. Thestructure of I is thought to be as shown, based on its infrared spectrumand the NMR spectrum of its phenylurethane derivative. Intermediate IIis relatively stable and suitable for herbicidal use, various type 11compounds showing qualitatively the same activity as the correspondingtype III compounds. The structure of II is not firmly established butpresent evidence favors the structure shown in the reaction dia grambelow.

o 01 o I RN Ndsonzhrronzsrr Niisorr2o H o1r,

R II R In \onaoom CHaCOCl/ R 0 J1 o Niisornonongs om R IV 3 On treatmentwith acetyl chloride both II and III give compounds (IV) having the sameNMR spectrum and, while this spectrum is not readily interpreted, and amixture of position isomers cannot be excluded, comparison with modelcompounds suggests the structure shown.

The success of this sequence of reactions leading to a thiolcarbamateapparently requires a secondary amine as starting material. In threeinstances in which a primary amine was used the crude productsdecomposed extensively and no epithiopropyl thiolcarbamate (III), wasobtained. In one experiment, starting with tert.-butyl amine,tert.-butyl isothiocyanate was found among the products ofdecomposition.

The final products (III) of the sequence-are distillable liquids orcrystalline solids. Some care must be exercised to prevent excessiveheating during distillation. Otherwise the following decompositionreadily occurs:

H at N( JSCHzC]-CH2 This thermal decomposition, if desired, may be usedas an efficient and probably the most economical method of Method 13 Asolution of 36 g. (0.173 mol) of diethylammonium diethyldithiocarbamateand 15.0 g. (0.162 mols) of epichlorohydrin in 100 ml. of dioxane isheated to reflux. Shortly after heating is begun, a crystallineprecipitate appears. After two hours, the solution is cooled andfiltered to recover 15.4 g. of diethylamine hydrochloride. The filtrateis vacuum distilled to remove the bulk of the solvent, leaving 33.2 g.of a viscous brown oil. Extraction of this oil with ether, decantationand evaporation of the ether gives 25.7 g. of residue, distillation ofwhich gives 17.7 g. of III, R,R'=Et.

In Table I are listed the compounds of type III prepared by the aboveprocedures.

TAB LE I thyl Percent yield l1718/0.4 mm.

Crude material, not distillable nu 1.5974. Crude material, notdistillable no 1.5773. 15766/0.10.9 mm.

Crude material, not distillable no 1.6142. Crude material, notdistillable 111) 1.5763. Crude material, not distillable 1m 1.5581.Crude material, not distillable no 1.5166. M.P. 55.5b8. b

129-31/0.s mm.

Crude material, not distillable no 1. 5500. M.P. 9615-98".

Crude material, not distillable no 1.5503.

Method Yield based on epichlorohydrin charged. Crude productcrystallized and was rccrystalllzed from hexane.

preparing allyl thiolcarbamate, which are products of establishedutility. (See, for example, British patent 808,-

(II) Illustration procedures Method A To a well-stirred mixture of 38.0g. (0.5 mol) of carbon disulfide and 46.3 g. (0.5 mol) ofepichlorohydrin in an ice-salt bath is added 36.5 g. (0.5 mol.) ofanhydrous diethylamine during 1-2 hours at to The mixture is stirred anadditional minutes, then let warm slowly to room temperature. At thispoint the reaction mixture is essentially 3-chloro-2 hydroxypropyl N,Ndiethyldithiocarbamate, (I; R,R'=Et), a viscous yellow oil with nodetectable unreacted starting materials present.

Heating of the reaction mixture for 2 hours at 8090 under vacuum gives110 g. of crude rearrangement product 11 (R,R'=Et). The course of therearrangement may be easily followed by the disappearance of infraredabsorption bands at 2.95 (OH) and l0.15,u (C=S) with the appearance ofbands at 3.92,u (SH) and 6.0;]. (0:0). The rearrangement is alsoaccompanied by a marked decrease in ViSCOSity.

(III) Herbicidal use Pre-emergent herbicidal activity was evaluated bymeans of the following procedure:

A solution was prepared by dissolving 290 mg. of the compound to betested in 200 ml. of acetone. Disposable paper half-flats were preparedand seeded, then sprayed with the acetone solution at the rate of 20pounds of active chemical per acre of sprayed area. One flat, Which hadbeen seeded with a1falta,brome, flax, oats, radishes and sugar beets washeld at 75 F. day temperature; another seeded with corn, coxcomb,cotton, crabgrass, millet and soybeans was held at F. Twenty-one daysafter seeding and treatment the flats were examined and plant emergenceand eflects on growth were rated according to the schedule set forthbelow.

Type of action: Degree C=chlorosis (bleaching) O=no effect. N==necrosisl=slight effect.

G=growth inhibition =moderate effect. F=formative eflect (abnormal formof growth) 3=severee1fect K=non-emergence 4=maximum effect (all plantsdied).

Following are tabulated the results of tests according 4. The compoundaccording to claim 3 in which R to the above procedures on arepresentative group of thiand R are ethyl substituents. olcarbamates.

' PRE-EMERGENT HERBICIDAL ACTIVITY Compound N S-CH2CHCH2 RI --I- Crab-Cox- Soy- Sugar- R R grass comb Brome Mlllet bean Cotton Alfalfa OatsCorn Flax Radish beet t 1 h G1 G1 "h E yl F1 0 K3 F1 0 G1 1 IsopropylIsopropyl G1 K4 G1 0 P 1 P 1 F2 i F3: G1 K4 F3 G1 G1 HexyL-.- e y m" 0.0 0 0 0 0 G2 G2 Butvl Ethyl F2 0 K4 F2 0 0 Isopropyl do n: CyclohexylIsopropyl Iwbutyl G3 G1 K4 G3 G1 0 G1 K4 0 0 0 G3 Isopentyl p 0v 0 0 0 00 0 0 0 0 o 0 1 K3 G1 G3 G3 G1 G2. G1 0 G2 0 o 0 G3 cyclqhexyln-u "a "65% "a 1 0 ii "a "a "6 "a Isopropyl Isopropyl Gg 0 K4 Gtz) 0 0 0 G3 0 0 00 Pmpyl Pmpyl F2 G1 K4 F2 G1 G1 0 F3 0 0 G1 0 Ethyl Isopropyl Gg 0 K4 G30 0 G0 G2 0 0 0 0 Bum Ethyl F2 0 F2 0 0 51 F3 0 o 0 G1 1 K3 cyclvhexylG3 G2 G2 G2 G1 51 G3 0 G2 G2 G2 1 Immltyl g; cg K4 01 0 01 G2 0 0 0 G21W1 Bum G2 G3 G2 "a "a G2 "Gi a a "a 2:;2 K2

Ally

0 G2 G2 G1 G1 G1 0 0 0 o 0 G2 The tabulated data indicate clearly thepronounced selectivity of the pre-emergent herbicidal action of thecompositions. Also demonstrated in the data is an absence of activitytoward the test species when the N-substituents contain a total oftwelve carbon atoms. Although lacking in the desired type of herbicidalactivity, the higher N,N- dialkylthiolcarbamates are useful for otherpurposes, particularly in corrosion-inhibiting formulations, alone or incombination with nitrogen bases of the polyamine type, and asfungicides. The compounds derived from the higher moiecular weightsecondary amines in general exhibit microbiolo'gical activity withoutsubstantial effect on plant 5. The compound according to claim 3 inwhich R and R are isopropyl substituents.

6. The compound according to claim 3 in which R and R are propylsubstituents.

7. The compound according to claim 3 in which R and R are butylsubstituents.

8. The compound according to claim 3 in which R and R are isobutylsubstituents.

9. The compound according to claim 3 in which R and R are allylsubstituents.

10. The compound according to claim 3 in which R lif is butyl and Rf isethyl.

\ivhat i laimed i The mpound according to claim 3 in which R isisopropyl and R is ethyl.

1". The method of producing an N,N-disubstituted thiocarbamate ester,wherein the N,N-su bstitutents are alkyl, cyoloalkyl or alkenylsubstituents containing a total of less than ten carbon atoms,comprising reacting an N,N- disubstituted dithiocarbamate salt withepichloro-hydrin.

2. The method of producing an N,'N-disubstituted thiolcarbamate esterwherein the N,N-substituents are alkyl, cycloalkyl or alkenylsubstituents containing a total of {12. The compound according to claim3 in which R is cyclohexyl and R is isopropyl.

13. The compound according to claim 3 in Which R is cyclohexyland R isethyl.

14. The compound according to claim 3 in which R is cyclohexyl and R ismethyl.

15. The compound according to claim 3 in which R is less than ten carbonatoms, comprising reacting at about butyl and is methyl- 0 C. asecondary amine with carbon disulfide and epi- R f Ct d chlorohydrin andheating the reaction product at about e erences 8090 C. UNITED STATESPATENTS 3. A compound represented by the structural formula 3 5 1 9492/1971 Doyle o H HENRY R. JILES, Primary Examiner NCSCHzCH-CH2 C. M.SHURKO, Asslstant Examiner US. Cl. X.R.

in which R and R are alkyl, cycloalkyl or alkenyl substituentscontaining a total of less than 10 carbon atoms. 75 N3. N0 X-refs.necessary. (see patent US. 3,510,290)

